Process for the dewaxing of oils



June 2, 1959 A. HoPPE ET Al.

PROCESS FOR THE DEWAXING OF OILS Y Filed Nov. 2l, 1955 2 Sheets-Sheet lJune 2, 1959 A. HoPPE ET AL PROCESS FOR THE DEWAXING OF` OILS 2Sheets-Sheet 2 Filed Nov. 2l, 1955 United States Patent() PROCESS FORTHE DEWAXING OF OILS Alfred Hoppe and Hermann Franz, Frankfurt am Main,Germany, assignors to Edeleanu Gesellschaft m.b.H., Frankfurt am Main,Germany l Application November 21, 1955, Serial No. 548,227

Claims priority, application Germany November 26, 1954 4 Claims. (Cl.208-25) 'Ehe present invention relatesto a continuous process for theremoval of aliphatic compounds such as paraflinic waxes from hydrocarbonoils.

Extensive experimentation has established that urea forms solidcompounds or adducts with straight-chain parain hydrocarbons.Derivatives of the straight-chain parailins, for instance olens, oxygen,nitrogen, sulfur and halogencontaining substances, will similarly enterinto this rreaction with urea, provided that they do not contain longside chains.

While urea CO(NH2)2 forms adducts with straight; chain paratiins andtheir derivatives, thiourea CS(NH2)2 forms adducts with branched-chainparains and naphthenes under conditions similar to those for adductformation between urea and n-parains.

In order to produce the adducts, the liquid paraiiins or theirderivatives are brought into contact with urea; the solid adductproduced is separated from the nonadduct forming substances and (1) byheating to elevated temperatures or (2) by the addition of solvents isreconverted into parafns on the one hand and (1) the urea or (2) asolution thereof on the other hand. The parains form the one finalproduct and the non-adductforming substances the other iinal product;the urea or thiourea solution is used again for further formation ofadduct. The temperature of the adduct formation depends upon the size ofthe molecules of the hydrocarbons and is generally between -lO and +50C. The quantity of urea to be used also diiers; it increases with thelength of the chains and is an average of 3 parts by weight of urea. tol part by weight of paraiiin. The commencement and duration of theadduct formation is activated by the presence of solvents for the urea.As such, there may be used water and/ or water-miscible solvents, e.g.lower alcohols such as methanol and ethanol, ketones such as acetone,and the like. The quantity of the solvent, the so-called activator,varies within wide limits since the urea may lbe used as a saturated orsupersaturated solution or as a paste wetted with solvent. Viscous andparain-rich oils are diluted with solvents which have a good dissolvingpower for the oil to be treatedbut not for the adductsuch as benzene,naphtha, organic halogen compounds, and the like.

For the sake of brevity, as used hereinafter, the removal of paraiflnsor dewaxing embraces both the formation of an adduct of urea withn-parains or their derivatives, and of thiourea with isoparains,naphthenes or their derivatives.

The speed with which the adduct is formed, as. well as the quantity ofparaffin taken up through formation of the adduct, is also dependentupon the quantity of the adduct former available. Assuming that it isdesired to remove a predetermined amount of paraiinic hydrocarbons orwaxes from an oil to bring the pour point to a predetermined value,there would be employed three times as much urea by weight as contrastedwith the parafln. Completion of `the reaction would require ICCextremely long contact periods which would make a continuous processimpractical.

The major portion of the parans or waxes readily enters into adductformation. The balance of the paraiiinic materials, often as low as 5%of the total paraiiinic content, requires several hours and oftenseveral days until it is completely combined as an adduct.

The lower the pour point of an oil, the greater will be the influenceexerted on such pour point even by small quantities of waxes ofparaflinic nature. Thus, for instance, the presence of 1% paraiin has aninsignicant effect on the pour point of an oil when the pour point is 10C., for instance. However, the same quantity of parafnic wax increasesthe pour point several degrees when the pour point of the oil is between15 C. and 20 C. It is therefore necessary that the parain content bereduced to a predetermined level in order to obtain the desired pourpoint, and commercial necessity requires that this is effected in aminimum amount of time.

To this end it is possible to add the urea in excess of the quantitytheoretically required for adduct formation with all the parain to beremoved. The reaction under such conditions will be terminated at suchltime as it is calculated will be required for the predetermined quantityof parain to be combined through adduct formation. It is clear that atthis time, however, not all of the urea will have entered into adductformation and thus will pass through the process unchanged. The overalleiect is to reduce the amount of oil which can be treated in equipmentof a given volume, to increase the cost of urea for a given dewaxingoperation, and

otherwise to increase the cost of obtaining oil of thev desired pourpoint.

In accordance with the present invention these disadvantages are avoidedand overcome, the novel process being rapidly conducted Without the useof excess urea. The urea or thiourea is contacted with theparaffincontaining oil in stages, i.e., in the first stage untreated oilis contacted with an adduct still containing some unco-mbined urea. Inthe nal stage, the pre-treated oil is contacted with fresh urea orregenerated urea respectively, the products constituting the oil ofdesired pour point and an adduct phase containing uncornbined urea whichis sent to the rst stage for reaction With fresh oil.

In this manner, in the rst stage `the free urea still present in theadduct is rapidly combined with those components of -the untreated oilwhich have the greatest tendency to form adducts. In the final stage,the oil from which the most reactive components have been removed iscontacted with fresh urea in excess of the quantity required to removelthe remaining paraiiins from the oil. As a result the parafns are takenup quickly and the excess urea serves for the pre-treatment of furtheroil.

The invention will now be described with reference to the accompanyingdrawings, wherein:

Figure 1 is a How-sheet of a process conducted without temperaturecontrol; and

Figure 2 is a How-sheet of a modied process conducted with individualtemperature control during the separate stages of the reaction.

Referring now to the process described schematically in Fig. 1, anadduct of urea with straight-chain parans or their `derivatives andcontaining unreacted urea is passed from iilter 10 through conduit 11into mixer 12. Fresh oil, containing straight-chain paraflinic waxeswhich it is desired to remove, is introduced through conduit 13 into themixer 12 where -it is permitted to contact the unreacted urea carriedalong with the adduct and introduced through conduit 11. Theparaiinic'com-r pounds having the greatest alinity` for the ureaf0r`11i- 3 adducts with the urea until the urea is completely exhaustedthrough adduct formation.

The suspension of adduct and oil still containing some parainicmaterials, is passed through conduit 14 into a centrifuge 15 where theoil is separated vfrom the solid adduct. The adduct is preferably passedthrough washer 16 and' then to the decomposer 17 where upon addition ofurea solvent through conduit 27 it is broken down into paratiinic Waxand urea solution.

The parathnic wax is removed from the system through conduit 20. Theurea solution is drawn ofi through conduit 19 and is transferred to athickener 26. The excess of urea solvent is evaporated, condensed andrecycled to the `decomposer 17 through conduit 27.

The urea solution, regenerated in the thickener 26 is admitted intomixer 21 through conduit 28, pre-treated oil from centrifuge 15 alsobeing admitted into mixer 21 through conduit 22. From the mixer 1 theslurry of adduct and oil solution then passes via conduit 23 to thefilter 10. The adduct which precipitated as a solid` is separated fromthe solution of dewaxed oil and oil solvent, the adduct being recycledthrough conduit 11. The solution of oil and oil solvent introduced inthe evaporating system 24 is heated to evaporate the oil solvent bymeans of an evaporator 24 and the finished oil is pumped into a storageVessel or tank 25. The evaporated oil solvent is condensed and recycledthrough conduit 18 to the washer 16. The wash-iiltrate containing someoil is recycled through conduit 29 into the mixer 12.

The quantity of urea passing through the system per cycle is thatcalculated to react with the paranic waxes whose removal is desired,ie., three times the weight thereof. In the event that the compositionof the fresh oil Varies, this can be compensated lfor by changing therate of introduction of fresh oil and hence of paraftlnic waxes, orpreferably it is compensated for by either adding further quantities ofurea or by removing a portion of the urea solution formed in thedecomposer 17.

The process is equally elective using urea for the separation ofstraight-chain paraiiins and their essentially straight-chainderivatives, or using thiourea for the separation of branched-chainparains or naphthenes and their derivatives. If desired, heat can beemployed to effect the decomposition of the adduct in decomposer 17.

The process may also be etlected in a multistage countercurrentoperation wherein temperature con-trois are provided, as shown in Fig.2. Adduct containing excess urea is introduced from conduit 26 intomixer 27 and there stirred with fresh oil introduced through con- I duit28, the fresh oil containing straight-chain paraffnic waxes which it isdesired to remove. The contents of the mixer 27 are cooled byevaporation of solvent from the mixer, evaporation being eiected by pump29 which draws ott solvent vapors via conduit 30 and introduces thevapors into conduit 37.

The paraffin components exhibiting the greatest ainity for the ureareact with the urea until the urea is fully exhausted, the reactionoccurring substantially instantaneously. The slurry consisting of adductand oil solution is conducted Via conduit 31 into centrifuge 32 where itis separated into solid adduct and oil, the adduct leaving throughconduit 33 while the oil leaves through conduit 34. The adduct is washedin washer 35 and then passes to decomposer 36, in which the adduct isdecomposed to paraftinic wax and urea solution.

The parainic wax is withdrawn through conduit 38. The urea solutionhowever, is passed through conduit 39 into thickener 50, where theexcessive urea solvent is evaporated, condensed and then recycledthrough conduit 51 to the decomposer 36, while the regenerated ureasolution passes to the mixer 45 through conduit 52.

Theoil leaving the centrifuge 32 through conduit 34 passes into a secondmixer 40 Where it is reacted with adduct, containing, more urea, than inthe firstv stage, this .4. adduct being introduced through conduit 41.The remaining parains react with the urea and the slurry is passedthrough conduit 42 into centrifuge 43. The adduct together with urea andsome solvent is separated and returned through conduit 26 to the rstmixer 27. The oil passes oi through conduit 44 into the third mixer 45which is also supplied with the regenerate-d urea solution throughconduit 52 leading from the thickener 50.

From the third mixer, wherein the regenerated urea forms an adduct withthe residual paratiinic waxes in the oil which has already passedthrough two treatment stages, the slurry passes through conduit 46 intoiilter 47. The adduct plus urea which is filtered ott together with someadherent urea solvent is passed to the secon-d stage through conduit 41while the dewaxed oil together with the major portion of the oil solventpass into evaporator 48 wherein the solvent is distilled oit andreturned to conduit 37 for use in the washer 35. The oil is then passedtothe tank 49.

The Wash-ltrate containing some oil is passed through conduit 53 to themixer 27 in order to dilute the fresh oil.

The fresh oil was cooled initially but the temperature is allowed torise freely during the processing so that the oil temperature increasesin passing through successive stages. By adjusting the feed rate of theoil and hence of the paraiiinic waxes so that the urea is present in thecalculated amount ratio per unit of time there will be no deadweight onthe process as would otherwise be realized by employing urea in largeexcess over the amounts required, in an effort to speed up the reaction.In spite of the fact that the feed rate of `fresh oil is so great thatthe rate between parain and urea is calculated the reaction rate is notimpaired. As a consequence, a greater quantity of oil can be handled ina given apparatus. Moreover, since a large measure of the processingcost involves power expenses for pumping the materials, the fact thaturea is not carried through the process as deadweight represents afurther and considerable economy.

The following examples are illustrative of operations employing theequipment shown in the drawings:

Example I In a typical run employing the apparatus of Fig. 1, urea wasemployed for dewaxing a spindle oil of Kuwaitv origin containing 9.5% byweight of parafins. To bring the oil to the desired pour point, it wasnecessary to remove about grams of paratn wax per liter of oil. Thesystem was operated at a rate such that 30 grams of urea dissolved inwater were discharged from the thickener per second. The feed rate wastherefore adjusted to 0.11 liters per second, i.e., substantially 3grams of urea being recycled for each gram of paraffin Wax introduced.The paratiin wax was removed in the desired amount when running theapparatus over a period of one hour. The pour point of the raliinate was20 C.

Example II The apparatus of Fig. 2 was fed with an oil containingbranched-chain paraiiins. To obtain the desired pour point it wasnecessary to remove 18 grams of wax per liter of oil. The process wasconducted with thiourea, the regeneration rate of thiourea in thethickener amounting to 30 grams per second, dissolved in Water. The feedrate of the oil was therefore adjusted to .55 liter per second. Thetemperature of the slurry leaving thefirst mixer was 10 C., thetemperature leaving the second mixer was 18 C., and the temperatureleaving the third mixer was 23 C. The calculated amount of .parathn wasrecovered per unit of time, the dewaxed oil exhibiting the desired pourpoint.

Various changes and modifications may be made without departing from thespirit and scope of the present invention and it is intended that suchobvious changes andmodicationsbe embraced by the annexed claims..

What is claimed is:

1. The process for the dewaxing of oils comprising the steps of treatingan oil in successive stages with a material selected from the groupconsisting or urea and thiourea at temperatures of between about C. andabout +50 C., and employing in the last stage a fresh quantity of saidmaterial in substantially the amount necessary to remove the desiredquantity of paranic waxes from the fresh oil introduced in the firststage, said material forming an adduct with some of said parainic waxesin each stage, separating the oil from the 'adduct and any unreactedmaterial in each stage, said adduct in all stages except the firstcontaining unreacted material, passing said adduct with unreactedmaterial in each stage except the rst stage to the preceding stage thereto be used for dewaxing of the oil, removing the oil dewaxed to thedesired degree from the last stage, and removing the adduct from thefirst stage.

2. The continuous process for the dewaxing of oils comprising the stepsof continuously passing an oil through successive stages, treating theoil in each stage with a material selected yfrom the group consisting ofurea and thiourea at temperatures of between about 10 C. 'and about +50C. and employing in the last stage fresh material continuouslyintroduced in substantially the amount per unit of time necessary toremove the desired quantity of parainic waxes introduced with the freshoil in the rst stage in said time unit, said material in each stageforming an adduct with some of said parainic waxes in each stage,continuously separating the adduct and any unreacted material from theoil in each stage, the adduct in all stages except the first containingunreacted material, continuously passing said adduct with unreactedmaterial to the preceding stage there to be used for dewaxing of theoil, continuously removing oil dewaxed to the desired degree from thelast stage, continuously removing the adduct from the lirst stage,continuously decomposing said adduct to regenerate said paraliinic waxesand said material, continuously withdrawing said paraflinic waxes, andcontinuously recycling said material to said last stage.

3. The process of claim 2, wherein said parainic waxes are essentiallystraight-chain hydrocarbons and derivatives thereof, said materialhaving the formula CO(NH2)2.

4. The process of claim 2, wherein said parafiinic waxes are essentiallybranched-chain hydrocarbons and derivatives thereof, said materialhaving the formula CS(NH2)2.

References Cited in the le of this patent UNITED STATES PATENTS2,499,820 Fetterly May 7, 1950 2,695,283 Lynch Nov. 23, 1954 2,723,220Axe Nov. 8, 1955

1. THE PROCESS FOR THE DEWAXING OF OILS COMPRISING THE STEPS FO TREATINGAN OIL IN SUCCESSIVE STAGES WITH A MATERIAL SELECTED FROM THE GROUPCONSISTING OF UREA AND THIOUREA AT TEMPERATURES OF BETWEEN ABOUT-10*C.AND ABOUT +50*C., AND EMPLOYING IN THE LAST STAGE A FRESH QUANTITY OFSAID MATERIAL IN SUBSTANTIALLY THE AMOUNT NECESSARY TO REMOVE THEDESIRED QUANTITY OF PARAFFINIC WAXES FROM THE FRESH OIL INTRODUCED INTHE FIRST STAGE, SAID MATERIAL FORMING AN ADDUCT WITH SOME OF SAIDPARAFFINIC WAXES IN EACH STAGE, SEPARATING THE OIL FROM THE ADDUCT ANDANY UNREACTED MATERIAL IN EACH STAGE, SAID ADDUCT IN ALL STAGES EXCEPTTHE FIRST CONTAINING UNREACTED MATERIAL, PASSING SAID ADDUCT WITHUNREACTED MATERIAL IN EACH STAGE EXCEPT THE FIRST STAGE TO THE PRECEDINGSTAGE THERE TO BE USED FOR DEWAXING OF THE OIL, REMOVING THE OIL DEWAXEDTO THE DESIRED DEGREE FROM THE LAST STAGE. AND REMOVING THE ADDUCT FORMTHE FIRST STAGE.